Multiple-position power-operated examination tables and chairs are known in the art as disclosed, for example, in U.S Pat. Nos. 4,168,099, 2,042,399, 3,754,749, 3,041,120, 3,281,141, 3,578,379, 3,241,828 and 3,206,188. Such supporting structures may be properly referred to as tables because of their capability of supporting patients in reclining positions; however, they may also be regarded as chairs because they may be adjusted to support patients in seated positions. For consistency, the term "table" will be used throughout this specification, it being understood that such term is not intended to exclude structures also capable of functioning as chairs.
Such a table must not only be adjustable into a wide variety of elevations and angular positions but must also provide a firm and stable support for a patient during examination and/or minor surgery. For these and other reasons the tops of such tables tend to be heavy. To such weight may be added the weight of a patient supported by the top and, at least in some cases, the downward force exerted by the power drive during a lowering operation. Should the limb of a doctor, nurse, or assistant become trapped beneath the top as it descends under power, or should the descending top engage a table, stand, or surface supporting medical fluids, instrumentation, or other types of medical equipment and supplies, a dangerous condition might readily develop. The problems and dangers tend to be increased by the frequent need to have related medical equipment close at hand, the common occurrence of two or more medical practioners or workers in close proximity to the table, some of whom may be seated at the time the position of the table is changed, the multiplicity of positions and adjustments of which such tables are capable, and the common provision of a foot control unit, often positioned directly beneath the table, for controlling the power to shift the table into its various positions of adjustment. Accidental operation of such a foot controller might easily cause a conventional power-operated table to descend in a way that could result in injury to the operator or to others, or damage to surrounding equipment.
A main aspect of this invention therefore lies in providing a power-operated multi-position medical table which avoids the dangers and disadvantages described above. Specifically, should the table top engage an object as it descends under power, and should the resistance to downward movement equal or exceed the weight of one of the hinged outer portions of the top and the weight of the patient supported by that portion, the hinged section will be free to pivot upwardly because of the resistance imposed by the obstruction even as the power drive for the hinged section continues to operate, and even if the support column for the entire top is retracting under power. Should the resistance to downward travel be great enough to exceed the weight of the top as a whole, combined with the weight of the patient, then the top in its entirety ceases downward travel and power is automatically interrupted.
The power-operated table (chair) has a pedestal and an articulated top supported by that pedestal, the pedestal consisting essentially of a base and an extendable/retractable column mounted upon that base. The column has a plurality of telescoping sections including an upper section connected to the top and a lower section mounted upon the base.
In a preferred embodiment of the invention, the column contains at least one vertically-elongated threaded shaft which is rotatably supported at its lower end upon the base and which may be selectively driven in one direction or the other about its longitudinal axis by means of a reversible motor. An elongated vertical tube, which is operatively connected to the top and constitutes an extension thereof, receives the threaded shaft and has its lower end resting upon a load-bearing member threadedly carried by the shaft. Power rotation of the shaft results in the load-bearing member, tube, and top traveling upwardly or downwardly depending on the direction of shaft rotation. A sensor is mounted to move vertically with the top (in the disclosed embodiment, the sensor is mounted upon the vertical tube) and cooperates with the load-bearing member to detect separation of the load-bearing member from the tube should descent of the top be obstructed by someone or something during a lowering operation, and to immediately interrupt the power drive system upon detection of such separation.
In the disclosed embodiment, two sets of threaded shafts, tubes, and load-bearing members are provided within the extendable/retractable column. Each load-bearing member takes the form of a nut having a support flange at its lower end and a beveled upper surface for engaging the lever arm of a sensing switch to close or open the power circuit during a lowering operation depending on whether the top is or is not supported by the load-bearing members. Means are provided for preventing rotation of each nut within its tube and for limiting the extent of relative axial movement of the tube and nut. Contact between the switch arm and the nut occurs through a side wall opening in the tube. Ideally, the tube is rectangular (square) in cross section. A liner or sleeve may be disposed within the tube and about the threaded shaft to prevent wobbling, reduce noise, and insure smooth operation during extension and retraction of the top.
The articulated top includes an inner or central section that is mounted upon the upper section of the telescoping column. It also includes at least one outer section that is hingedly connected to the central section along a horizontal hinge line. One such outer section may take the form of a hinged back section; another may constitute a hinged legrest section. Auxiliary power means may be provided for pivoting each hinged outer section between a lowered position and any of a variety of raised positions, the auxiliary power means including a second motor for extending and retracting a second load-bearing member. When the motor is operated to extend the second load-bearing member, that member bears against a stop member carried by the other hinged section to pivot that section into its raised condition; conversely, when the load-bearing member is retracted, the hinged section is permitted to lower under its own weight. Should that section of the top engage an obstacle as it descends, the resistance imposed by the obstacle will block further downward movement of the hinged section even though operation of the auxiliary power means continues.
Other features, objects, and advantages of the invention will become apparent from the drawings and specification.